The purpose of this research is to determine the heterogeneity of rat hepatic UDP-glucuronyltransferase. Lubrol-extracted UDP- glucuronyltransferase will be further purified with the aim of physically separating activities toward o-aminophenol and p-nitrophenol. Methods to be employed include gel filtration, sucrose density centrifugation and affinity chromatography. Characterization of the enzyme and enzyme kinetics will be determined in purified preparations to determine if differentiation of multiple forms of UDP- glucuronyltransferase can be made on the basis of their catalytic behavior. Similar studies will be done on purified UDP- glucuronyltransferase obtained from 3-methylcholanthrene-induced rats to determine if qualitative changes occur in the induced enzyme. Particular attention will be paid to the Michaelis constants of UDP- glucuronic acid, the common substrate for all glucuronyltransferases. Finally, the development of UDP-glucuronyltransferase will be determined in rats of various ages. That is, the sequence of appearance of activity toward each of the substrates will be assayed with the aim of ascertaining whether or not there is a non-synchronous appearance of activity toward the different substrates. Purified enzyme will be used.